(a) Field of the Invention
The present invention relates to a braking device for the ladder lifter of a fire-fighting or high-altitude working extensible ladder truck.
(B) Description of the Prior Art
The conventional braking device comprises a hook lever pivotally mounted on a crosspiece of a ladder. Normally said lever is locked in its retracted position on the lifter side, but when the lifting wire rope is broken, the lever is automatically released and swung into engagement with the associated crosspiece, thereby preventing the lowering of the lifter. According to this arrangement, although it is possible to stop the lifter in this manner by making use of the constant spacing between adjacent crosspieces of the ladder when the rope breaks, it sometimes occurs that the lifter falls through a distance up to said crosspiece spacing from the position assumed by the lifter when the rope breaks, giving the rider a great shock or a feeling of uneasiness.